HipPiE · Hippo signalling Pathway in Endosymbiosis

The rice weevil Sitophilus oryzae is a pest insect which can cause major damages to cereal crops worldwide. S. oryzae hosts an endosymbiont, the intracellular gram-negative bacterium Sodalis pierantonius, which produces amino acids necessary for the host’s cuticle thickening. This biological interaction, called nutritional endosymbiosis, generally increases the weevil’s fitness, for example as a thicker cuticle protects the host against desiccation. Consistently, the bacterial load in S. oryzae has been shown to fluctuate throughout the development, with a peak in young adults, at the same time as cuticle thickening. However, maintaining endosymbiotic bacteria also constitutes an energetic cost for the host, and after the peak in young adult weevils, S. pierantonius load decreases. As the endosymbiont is present in specialised cells (i.e., bacteriocytes), organised in organs (i.e., bacteriomes), regulation of S. pierantonius load relies on a strong coordination between the two partners. The HipPiE project aims at investigating further the regulation of the endosymbiont dynamic, in order to find new sustainable strategies for pest management, using symbiosis disruption. By using dual transcriptomics at different developmental stages in S. oryzae, a recent study from the host team showed that several genes from the Hippo signalling pathway were differentially expressed in young symbiotic adult weevils as compared to weevils with no endosymbiotic bacteria (aposymbiotic weevils), suggesting a role of this pathway in the endosymbiont dynamic. The Hippo signalling pathway is involved in several biological responses like growth, cell differentiation, cell death, and tissue regeneration. However, its role in endosymbiosis has not been studied yet. During this project, we will study the role of the Hippo signalling pathway in the regulation of the endosymbiont load in young adult weevils, using interference RNA, flow cytometry, imaging and transcriptomics.